Filters with echogenic characteristics

ABSTRACT

There are described a variety of intravascular filters have wherein at least a portion of the filter has been modified to provide an enhanced echogenic characteristic of the filter.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/785,204, filed Mar. 14, 2014, which is herein incorporated by reference in its entirety.

INCORPORATION BY REFERENCE

All publications and patents and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference.

FIELD

Aspects of the invention described herein relate generally to filters inserted into a patient's body and more particularly to the provision of echogenic coatings on such devices to enhance their visibility using one or more of in any combination ultrasound imaging, intravascular ultrasound imaging, greyscale intravascular ultrasound imaging, color intravascular ultrasound imaging or ultrasound image signal processing that included spectral analysis.

BACKGROUND

Ultrasonic imaging in the medical field is widely used for a variety of applications. In addition to imaging physiological structures and tissue such as organs, tumors, vessels, and the like, it is often desirable for a physician or technician to have an image of a medical device which has been inserted into the tissue or passageway of a patient. Still further, advancements in the use of intravascular or intraluminal imaging ultrasound (positioned either within or outside of the body) before, during and after procedures has led to increasing requirements for cooperation between device and imaging modality.

A variety of approaches have been used to enhance ultrasonic imaging of devices by increasing the acoustic reflection coefficient of the devices. While echogenic materials have been described for some uses in medical devices, the conventional uses of echogenic materials has not kept pace with the advancements in applications for imaging ultrasound. Moreover, while many approaches have been attempted, there is still need for improvements that are particular to the use of specific device designs. In particular, as medical therapies and procedures continue to advance, there is, in many medical instances, a need for more specific information about a device, its placement, position, orientation or aspect in relation to another object. What is needed are further improvements to the manner and placement of echogenic enhancements to obtain these additional benefits.

SUMMARY OF THE DISCLOSURE

In general, in one embodiment, a filter includes a hub; and a plurality of legs or wires or segments extending from the hub; wherein at least a portion of the hub or a portion of one or more of the legs or wires or segments is modified to provide an enhanced echogenic characteristic of the filter.

This and other embodiments include one or more of the following features. In one aspect, the modification can provide an enhanced echogenic characteristic of the filter is a modification to a portion of the filter to enhance the echogenic characteristics of that portion of the filter. In another aspect, the modification can provide an enhanced echogenic characteristic of the filter which can be the formation of dimples into a surface of the filter. In yet another aspect, the dimples can be of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with an intravascular ultrasound system. In a further aspect, the modification can provide an enhanced echogenic characteristic of the filter which can be the formation of protrusions formed in, placed on or joined to a filter surface. In an additional aspect, the protrusions can be of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with an intravascular ultrasound system. In another aspect, the modification can provide an enhanced echogenic characteristic of the filter including the roughening one or more surfaces of a filter. In yet another aspect, the roughening can be performed using a chemical process, a laser or bead blasting technique. In still a further aspect, the roughening can be of sufficient scale to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems. In a further aspect, the modification can provide an enhanced echogenic characteristic of the filter including altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of the filter. In an additional aspect, the cavities, voids or pockets can be of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with an intravascular ultrasound system.

This and other embodiments include one or more of the following features. In one aspect, the filter can further include at least one fixation element. Any portion of the tissue anchor or any portion of one of the hub, the plurality of legs or wire or segments extending from the hub can be modified to provide an enhanced echogenic characteristic of the filter related to the use, status, position orientation of the at least one fixation element or the filter. In another aspect, the first and second support members, the crossover and the first end or the second end of the first support member, any portion of one of the above can be modified to provide an enhanced echogenic characteristic of the filter related to the use, status or of clot burden of the filter. In a further aspect, a method of positioning a filter within a lumen can include advancing a sheath containing a filter through the lumen, deploying a portion of the filter from the sheath into the lumen while maintaining a portion of the filter within the sheath, either of the above steps can be performed before or after using imaging from an intravascular ultrasound system. In an alternative aspect, a method of deploying a filter within a lumen can include advancing a sheath containing the filter through the lumen; and deploying the filter into the lumen, wherein, either step can be initiated, performed, confirmed or completed at least in part based on information obtained using intravascular ultrasound from one or more echogenic aspects of the filter. In yet another aspect, the method can further include maneuvering a snare towards the filter in a direction to retrieve the filter and engaging the snare with the filter. The maneuvering step or the engaging step can be initiated, performed, confirmed or completed at least in part based on information obtained using intravascular ultrasound from one or more echogenic aspects of the filter. In still another aspect, the method can further include engaging the lumen wall with a fixation element attached to the filter. This step can be initiated, performed, confirmed or completed at least in part based on information obtained using intravascular ultrasound from one or more echogenic aspects of the filter. In one aspect, a filter delivery catheter can be adapted and configured to deliver a filter according to any of the previously mentioned embodiments. A delivery catheter can be adapted and configured for delivery of an endoluminal filter, an IVUS transducer can be integrated into the distal portion of the delivery catheter, and one or more connectors on the proximal end of the delivery catheter can be adapted and configured to connect the IVUS transducer to an appropriate imaging or processing system. In another aspect, the filter delivery catheter can further include a telescoping sleeve within an moveable relative to the filter delivery catheter. In yet another aspect, the filter delivery catheter can further include a pusher rod within a moveable relative to the filter delivery catheter. In still another aspect, the IVUS transducer integrated into the distal portion of the delivery catheter can be adapted and configured whereby advancing and retracting the delivery catheter generates a plurality of images slices from the IVUS transducer. In a further aspect, the IVUS transducer integrated into the distal portion of the delivery catheter can be adapted and configured whereby advancing and retracting the delivery catheter can provide an output from the IVUS transducer for positioning guidance of a filter delivered using the delivery catheter. Is an alternative aspect, the IVUS transducer can be integrated into the distal tip or end of the delivery catheter. In yet another aspect, the delivery catheter can further include a pressure transducer. In still another aspect, the pressure transducer can be located proximal to the IVUS transducer. In one aspect, the delivery catheter can further include a filter as in any of the previously mentioned embodiments within the delivery catheter. In another aspect, a method of positioning a filter within a lumen can include advancing a delivery catheter according to any of the previously mentioned embodiments and can contain a filter as in any of the previously mentioned embodiments through the lumen using imaging information provided by the IVUS transducer on the delivery catheter to determine relative position before deploying a portion of the filter from the delivery catheter into the lumen to engage the lumen wall. In yet another aspect, the method can further include obtaining IVUS imaging of the lumen using the delivery catheter prior to deployment of the filter, after the deployment of the filter or during the deployment of the filter. In still another aspect, the method can further include obtaining IVUS imaging of the lumen using the delivery catheter for imaging a deployment location and estimating the sizing of a filter for the deployment location prior to performing any of the previously mentioned methods. In a further aspect, the method can further include estimating treatment duration using imaging data collected as in any of the previously mentioned methods. In an alternative aspect, a filter can further include an IVUS transducer integrated into the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

FIG. 1 is a section view of a wire strut or support element of a filter (w/s/s) having multiple segments in a concentric arrangement.

FIG. 2 is an embodiment of a segment having one or a plurality of laser drilled holes formed therein.

FIG. 3 is an embodiment of a segment having one or a plurality of raised features or alternatively roughed portions formed thereon.

FIG. 4 is an embodiment of a segment having one or a plurality of bubbles formed therein.

FIG. 5 is an embodiment of a segment having one or a plurality of dimples formed therein.

FIG. 6 is an embodiment of a segment having a coil or braided structure within or about the segment.

FIG. 7 is an embodiment of a segment having a plurality of echogenic markers arrayed in rings about the segment to provide an indication of measurement via the spacing between adjacent rings.

FIG. 8 illustrates various alternative configurations for a segment used alone or in conjunction with other segments.

FIG. 9 is a view of an exemplary filter illustrating various alternative aspects of providing a filter with improved echogenic characteristics.

FIG. 10 is an end view of the filter as it appears looking toward the apical hub forming a part of the filter.

FIG. 11 is a sectional view through the center of the apical hub forming a part of the filter, and illustrating the manner in which the legs of the filter are positioned in the apical hub and are retained therein.

FIG. 12 is a side view of an embodiment of the blood clot filtration device.

FIG. 13 is a perspective view of a vena cava filter embodiment showing the head and legs thereof.

FIG. 14 is a perspective view of a vena cava filter showing the head and legs thereof.

FIG. 15 is a perspective view of a thrombus filter.

FIG. 16 is a plan view of the anchor portion of a thrombus filter.

FIG. 17 is a schematic representation of a removal process for use with a thrombus filter.

FIG. 18 is a schematic representation of a thrombus filter drawn into the lumen of a removal catheter.

FIG. 19 is a fragmentary elevation view of the blood clot filter embodiment in a totally straightened position.

FIG. 20 is an elevation view of the blood clot filter in a partially straightened position.

FIG. 21 is a perspective view of a portion of the inferior vena cava and having a section removed to show the configuration of the blood clot filter in its implanted and anchored position within the inferior vena cava.

FIG. 22 is a perspective view of an alternative blood clot filter having two V-shaped struts and a tangle of fine wires.

FIG. 23 is a view of a filter in place in a vein.

FIG. 24 is a side view of a blood clot filter.

FIG. 25 is an embodiment of a filter in its unfolded state.

FIG. 26 is a side of the filter in an expanded position.

FIG. 27 is a view illustrating the filter by chain dot lines in a collapsed condition.

FIG. 28 shows schematically in perspective a filter its unfolded state.

FIG. 29 is an isometric view of a filter.

FIG. 30 is an elevation of a vena cava filter shown in its fully expanded state.

FIG. 31 illustrates an embodiment of a filter, seen in perspective.

FIG. 32 is a perspective view of a filter device, placed in position in a vein.

FIG. 33 is an isometric view of an embodiment of an embolus trap.

FIGS. 34A-34C illustrate an example of a guidewire having both a pressure sensor and an IVUS transducer located at the distal portion of the guidewire.

FIGS. 35A-35D illustrate two embodiments of an intravascular ultrasound catheter joined together in parallel with a catheter.

FIGS. 36A and 36B, the pressure sensor and/or IVUS transducer are integrated into a delivery catheter, a retrieval catheter or a device itself.

DETAILED DESCRIPTION

Filters are more complex structures in contrast to the relatively simple designs found in catheters and needles. In a more complex device like a filter there is a need to identify specific portions within the device during some medical procedures. In addition, it would be advantageous as well to determine the orientation of the device including components within the device to one another (as used for determining deployment, retrieval and the various intermediate stages thereof) as well as the overall filter orientation to the surrounding lumen or vessel. In contrast to the conventional techniques using location of the tip or start or end of the entire length, a more complex structure such as a filter position, orientation or relative placement information would yield specific benefits. In some cases, aspects, portions or attributes of the overall filter or filter components or portions will enable more useful determinations about the filter in relation to the physiological environment. In one aspect, an intravascular ultrasound (IVUS) catheter and processing system or signal processing algorithm is used to confirm filter sizing selection, guidance for filter placement, filter implantation steps, filter and/or vessel measuring using IVUS before during and/or after steps to confirm sizing selection and fit is appropriate under the physiologic environment and for confirmation and/or documentation of proper sizing selection, placement, engagement or degree of engagement of fixation elements (if present), clot burden, orientation and/or deployment in a patient or physician medical record.

In one aspect, embodiments of the present invention are directed toward medical devices having a complex shape or that are configured to move from stowed to deployed configurations that may also have specific orientation and placement criteria for proper use in a lumen, vessel or hollow organ. One such complex device is an IVC filter. Aspects of the present invention include such devices employed within the human body which have enhanced ultrasound visibility by virtue of incorporation of an echogenic material using any of the techniques described herein alone or in any combination.

In one aspect, there are described herein various alternative filter designs for increasing the echogenicity of the filter. A filter with enhanced echogenic characteristics may include one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. One example of the manufacturing alteration is to introduce gaps between the segments of tubing or coverings whereby the gap provides the echogenic enhancement. In addition, cavities, voids, pockets, dimples, gaps and the like may be left empty or, optionally, filed, partially filed or lined with any of the echogenic materials described herein.

In one aspect, there are provided embodiments of a filter having enhanced echogenic characteristics in or related to at least one or a portion of: an proximal end, a distal end, a terminal proximal end, a terminal distal end, a retrieval feature, an atraumatic tip on a retrieval feature, a mid-strut region, a leg or strut portion having at least one orientation attribute to another portion of the filter, an indicia of a location of a fixation element or a retrieval feature, a location on a portion of the filter selected such that in use with a particular fixation element the marker in in a location that indicates that the fixation element is fully deployed into a wall of a lumen or portion of a vessel or hollow organ (i.e., the marker is against the lumen wall or nearly so when the fixation element is fully engaged. As such, see the marker against the wall indicates proper deployment, spaced from or not visible would indicate, respectively, not fully engaged or over penetration); a portion of the distal tip and/or an elongated portion. The above described methods may also be applied to the other techniques and alternatives described herein.

In still further embodiments, a portion, component or aspect of an intraluminal filter may have enhanced echogenic attributes by applying a coating or sleeve containing one or more of the echogenic materials disclosed herein or fabricated according to any of the techniques or having any of the attributes to enhance echogenic qualities as described herein. In some aspects, the enhanced echogenic attributes are provided by the incorporation into, application onto or within a component or portion of a filter one or more echogenic materials or echogenic markers in a specific configuration, location, orientation or pattern on the filter.

Enhanced echogenic markers or locations may be devised and placed for use individually or in combinations such as to facilitate the identification to an IVUS system or ultrasound imaging modality an indication or signature for a specific location on a filter, such as, for example, a retrieval feature, a terminal proximal end, a terminal distal end, a location of a fixation element or a location of some other indicia that identifies a specific aspect of a particular filter design. In addition or alternatively, two or more enhanced echogenic markers or portions may be used in combination to provide additional information about a filter such as orientation with in a vessel, confirmation of deployment or a portion of a deployment sequence, confirmation of final placement, confirmation of migration or lack of migration, confirmation of retrieval or progress in a retrieval sequence and the like according to the various processes and used for filters within the vasculature or in lumens of the body. In another specific embodiment, the use of IVUS techniques with embodiment of the echogenic enhanced filters describe herein may also be used to measure the diameter of the vessel at specific device locations indicated by the echogenic markers during or after deployment or retrieval of a filter.

In still further aspects, the use of IVUS techniques with embodiment of the echogenic enhanced filters describe herein may also be used to determine, detect or indicate inadequate dilation, adequate dilation, filter expansion, degree of filter expansion, filter—vessel engagement and degree or engagement, strut/leg/anchor position and other attributes relating to the interaction between the filter and the surrounding physiological environment.

Still further, the echogenic markers are positioned with regard to the likely or planned positioning of the IVUS transducer and/or likely pathways for acoustic energy used by the imaging system. By way of example, if the IVUS transducer is forward looking, then those forward looking aspects of the filter will be provided with the enhanced echogenic aspects. In another example, if the IVUS transducer is cylindrically shaped and will be positioned through the interior portion of a filter then the filter will be provided with enhanced echogenic aspects on interior surfaces or portions that would receive acoustic energy from such as transducer in such a position. Other modifications are within the scope of the invention based on the particular style of IVUS transducer used, the position relative to the filter and the placement and type of echogenic feature incorporated into the filter. Put another way, the echogenic enhancements of the filters described herein are selected, designed and positioned on the filter with regard to the IVUS sensor type, acquisition mode and position relative to the filter. Additional details in the use of IVUS with filters is further described in U.S. Pat. Nos. 6,645,152 and 6,440,077, both of which are incorporated herein by reference in their entirety for all purposes.

In one aspect, the placement and signature of such enhanced echogenic markers are discernible to a human user viewing an ultrasound output alone or in combination with being discernible to a computer system configured for the processing of an ultrasound return including a return from the enhanced echogenic filter.

In various alternatives, the echogenic material may either be applied to a portion of or a component of a filter in any of a number of different techniques.

In one example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as a selective coating applied to a portion or component of a filter.

In one example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as a mold formed to be placed over or joined to a portion of component of a filter.

In one example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as an extruded sleeve formed in a continuous segment to cover a portion or component of a filter. In one embodiment, one of the inner tubular member or the outer sleeve or coating may be fabricated of a material according to the present invention, having increased echogenicity, with the other of the inner tubular member fabricated of a biocompatible polymer such as polyurethane or silicone rubber, for example.

In one example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as a compound or two layer structure comprising an inner tube and an outer tube or sleeve with one or both of the tubes made from or including or incorporating one or more echogenic materials or modifications as described herein. In addition or alternatively one or both sleeves, tubes described herein may include or encapsulate an echogenic marker or component of specific shape or geometry, for example, as in the case of a tube structure having within the sidewall of the tubing a coiled structure. In one aspect, the coiled structure is made from an echogenic material and the windings are provided in a manner that is useful in any of the aspects of the filter described herein. The coil may have a particular size or variation in size, pitch or variation in pitch or other attribute useful in providing an echo identifiable aspect of the filter property being determined. In one specific embodiment, the dimensions of the coil or other echogenic material has dimensions selected for increasing acoustic reflection with regard to the resolution or processing algorithms used in the imaging ultrasound system.

In one example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as a braided structure incorporated into a compound or two layer structure comprising an inner tube and an outer tube or sleeve with one or both of the tubes made from or including or incorporating one or more braid comprising echogenic materials or modifications as described herein. In addition or alternatively one or both sleeves, tubes described herein may include or encapsulate an braid formed into an echogenic marker or component of specific shape or geometry, for example, as in the case of a tube structure having within the sidewall of the tubing a braided structure. In one aspect, the braided structure is made from an echogenic material and the braided is a small diameter that is when wound around the tubes or sleeve or directly onto a portion of or component of a filter. The winding pattern and spacing of the braided materials are provided in a manner that is useful in any of the aspects of the filter described herein. The braid may have a particular braid strand composition, structure, size or variation in size, pitch or variation in pitch or other attribute useful in providing an echo identifiable aspect of the filter property being determined. One or more of the strands in the braid may be formed from an echogenic material. One or more of the strands may be formed from a material having improved radiopaque characteristic. One or more of the strands may be formed from a material having both echogenic and radiopaque properties. The strands of a braid may be combined using any of the above described strand characteristics.

In another alternative, in still another example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as the a series of short segments placed adjacent to one another along a portion or component of a filter in either a close packed or spaced arrangement. In another embodiment, the spacing or voids between adjacent segments may also be adjusted or selected so as to enhance echogenic capabilities of the filter using the material difference introduced by the spacings or voids.

In another alternative, in still another example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter as a tubing or sleeve suited to heat shrink operations. In one aspect, there is a manufacturing or assembly steps of sliding one or more sleeves over portion of the filter then apply heat to shrink down the segment about the portion of the filter. In particular, various embodiments provide for the specific placement of such a shrink fit tubing having enhanced echogenic characteristics as described herein. It is to be appreciated that the sleeves, segment or tubes may be provided from or have echogenic modifications or elements incorporated into suitable materials such as, for example, ePTFE, PTFe, PET, PVDF, PFA, FEP and other suitable polymers. Still further, these and other materials may be formed in shapes other than tubes but may also take the form of strands, lines, fibers and filaments to be applied in accordance with the echogenic enhancement techniques described herein. In some embodiments, the tubes or segments applied to a filter may have the same or different composition as well as have the same width or different widths. In one aspect, the width or thickness of a plurality of bands is used to provide a code or information about the filter. The use of echogenic bands of different widths is a marking technique similar to the way that different size and color rings on a resistor are arranged in a pattern to describe the resistor's value.

In another alternative, in still another example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter is extruded over a portion of or a component of the filter.

In another alternative, in still another example, an echogenic component or additive is applied to or incorporated into a filter or portion of a filter is by bonding an echogenic material or components to the filter using a suitable adhesive or bonding technique.

In any of the above described configurations, the portion or component of the filter may be modified with dimples, grooves, pockets, voids. In other aspects, there may be one or more full or partial circumferential recesses, rings, surface diffraction gratings or other surface features to selectively enhance or provide an echogenic property in that portion of the filter, to aid in or foster the application of the echogenic materials. In still further aspects, any of above described surface modifications may also be used to uniquely identify a portion of a filter or any of the above in any combination.

In still further aspects of any of the above echogenic markers or attributes the thickness of the sleeve or coating or component may decrease at its proximal and distal ends to provide for a smooth outer surface. As yet an additional alternative, a coating, marker or other echogenic material may extend proximally to or closely adjacent to the distal end or the distal end or both of the filter component or filtering device.

In still other alternatives or combinations, some filter design embodiments alter components of the filter to enhance echogenicity such as, for example, material selection to incorporate echogenic materials. Examples of echogenic materials include palladium, palladium-iridium or other alloys of echogenic materials.

In some embodiments, echogenic microbubbles are provided in a portion of a filter to enhance the acoustic reflections of that aspect of the filter. Echogenic microbubbles may be prepared by any convenient means and introduced into the component or portion thereof or by a coating or sleeve or shell or other transferring means or mixed with a polymer or other suitable base compound prior to extension of extrusion, molding casting or other technique. The echogenic microbubbles may be pre-prepared or prepared inside the component or element or marker as appropriate. Aspects of the preparation or use of microbubbles are described in U.S. Pat. Nos. 5,327,891; 4,265,251; 4,442,843; 4,466,442; 4,276,885; 4,572,203; 4,718,433 and 4,442,843. By way of example, echogenic microbubbles can be obtained by introducing a gas, e.g. carbon dioxide, into a viscous sugar solution at a temperature above the crystallization temperature of the sugar, followed by cooling and entrapment of the gas in the sugar crystals. Microbubbles can be formed in gelatin and introduced into a component or portion of a device. Microbubbles can also be produced by mixing a surfactant, viscous liquid and gas bubbles or gas forming compound, e.g. carbonic acid salt, under conditions where microbubbles are formed.

In still further alternatives, there is also the incorporation of dual mode materials (radiopaque and echogenic) into a polymer then used to form part of, be applied or otherwise incorporated with a filter device as described herein. Some of these polymer compounds may be fabricated to enhance aging and shelf life and have other beneficial attributes. In one aspect, a filter or portion thereof includes one or more selected segments that are constructed using visibility materials compounded with one or more polymeric materials that make the selected segments visible using both fluoroscopy and ultrasonic imaging. In one specific example, the visibility material may take the form of tungsten and/or tungsten carbide particles dispersed within a polymeric material. In one specific aspect, the radiopaque and echogenic material includes tungsten and/or tungsten carbide particles distributed within a base polymeric material.

In one embodiment, a portion of or a component of a filter includes or has been modified to have an inner layer including a radiopaque and echogenic material. In one alternative, the radiopaque and echo genic material includes particles distributed within a base polymeric material (i.e., a first polymeric material) including a polyether block amide; and an outer layer including an additional polymeric material (i.e., a second polymeric material). In certain embodiments, the additional polymeric material is a thermoplastic elastomer. Optionally, the additional polymeric material is more resistant to hydrolysis and/or oxidation than the base polymeric material.

In still further aspects, a component, a portion or an element added to a filter may be regarded as an echogenic body member that is a part of an echogenic filter to be sonically imaged. The echogenic body member is at least partially made up of a composite material which is echogenically imageable in the patient, such as by the use of ultrasonic imaging equipment used either within the patient or external to the patient. In one aspect, a composite material includes matrix material with discrete acoustic reflective particles embedded in matrix material. In one aspect, the matrix material is a biocompatible plastic. Examples of suitable plastics may include urethane, ethylene, silicone, polyethylene, tetrafluorethylene. In one aspect, a matrix is a formable, pliable material which may be molded and/or extruded to a variety of shapes, depending upon a specific application. The sound reflective particles are embedded in matrix material. Particles are, by way of example, made of a hard material, such as small glass particles that are solid or filled with an acoustically reflective medium. In one aspect, glass particles having a generally spherical shape forming glass microspheres. Glass microspheres with an outer diameter of about 5 microns is one acceptable size. Other sized particles may be utilized as, for example, ranging between 1 and 50 microns and beyond. Particles sized below the resolution size of the imaging ultrasound system in use may be arranged into patterns of sufficient size and orientation to the acoustic waves that result in a discernible feature by the imaging ultrasound system. Furthermore, the particles do not necessarily have to be spherical, or may be partially spherical. Still further, the shape of the particle could be altered to enhance acoustic reflection by presenting different shapes of particles, sizes of particles and combinations thereof to modify acoustic characteristics of the matrix material. By way of example, the particles may be shaped into an “Ordered array.” “Ordered arrays” can take the form of a macrostructure from individual parts that may be patterned or unpatterned in the form of spheres, colloids, beads, ovals, squares, rectangles, fibers, wires, rods, shells, thin films, or planar surface. In contrast, a “disordered array” lacks substantial macrostructure.

By way of example, an echogenic marker may comprise particles that individually are below the resolution of the imaging ultrasound system. The echogenic marker is the combination of these below imaging ultrasound resolution particles in combination, in 1D, 2D or 3D patterns, in graphic arrays, or in machine readable combinations to make a signature. Based on the specific characteristics of the combination of particles, the acoustic returns from an echogenic marker or combination of echogenic markers may be visually perceptible in a display for interpretation by a user or may be detected and interpreted by one or more acoustic reflection or spectral processing algorithms within a imaging ultrasound processing system.

In one aspect, the echogenic material is fabricated by incorporating nanometer sized particles of sonically reflective materials, for example iron oxide, titanium oxide or zinc oxide into a biocompatible polymer. In one method of fabrication, the acoustically reflective particles are mixed with a powdered thermoplastic or thermosetting material such as a polyether amide, a polyurethane or an epoxy, or polyvinylchloride followed by thermal processing of the mixture to provide a material of increased sonic reflectance which may be applied as a coating on medical devices of the type discussed above or may be incorporated as a structural component of the medical devices as described herein.

In still further embodiments and aspects, the particles included to provide echogenic enhancements may be selected, arranged or incorporated to provide acoustically geometrically tuned nanostructures, microstructures or macrostructures. The particles provided herein are formable in all shapes currently known or to be created for acoustic reflection enhancement. In non-limiting examples, the nano-, micro- or macro-particles are shaped as spheres, ovals, cylinders, squares, rectangles, rods, stars, tubes, pyramids, stars, prisms, triangles, branches, plates or comprised of an acoustically reflective surface or where one or more surfaces is adapted such as by roughening or dimpling or other technique used to alter acoustic reflection properties. In non-limiting examples, the particles comprise shapes and properties such as plates, solid shells, hollow shells, rods, rice shaped, spheres, fibers, wires, pyramids, prisms, or a combination thereof.

In one specific aspect, a partially spherical surface may be provided on the outside and/or the inside of particles, as for example a particle with a hollow spherical space therein. Particles are made up of a different material than the matrix. While desiring not to be bound by theory, it is believed that a spherical shape provides for sound reflections at a variety of angles regardless of the direction from which the ultrasonic sound waves are emanating from, and accordingly, are more likely to reflect at least a portion of the transmitted signal back to the ultrasonic receiver to generate an image. Since many of matrix materials available are relatively ultrasonically transparent in a patient, sound reflective particles provide adequate reflection. The use of a composite, rather than a solution, provides adequate size for acoustic reflection off of the discrete particles embedded in the matrix. As indicated, a variety of materials may be utilized for the sound reflective particles, such as aluminum, hard plastic ceramics, and, metal and/or metal alloys particles, and the like. Additionally, liquids, gases, gels, microencapsulants, and/or suspensions in the matrix may alternatively be used either alone or in combination, so long as they form a composite with the desired ultrasonically reflective characteristic.

Any of the above embodiments, alternatives or filter modifications to enhance echogenic characteristics may also be designed or implemented in such a way as to provide an echogenic identifiable or unique trait or acoustic reflection signature that may be registered by a human operator looking at a display or identified using signal processing techniques of a return containing acoustic reflections from the filter in an imaging ultrasound system. In one example, there is a surface of the filter having one or more echo registerable or identifiable feature, mark or indication in a position useful for determining one or more of: a location of an end of a filter; a location of a fixation element on a filter; a location of a retrieval feature on a filter; an orientation of one or more of a leg, a strut, a filter or an end of a filter relative to another of a leg, a strut, a filter or an end or the orientation of the overall filter to a lumen, vessel or hollow organ in a body. Moreover, in another widely applicable aspect of providing enhanced imaging characteristics to a filter as described herein, the characteristic or modification—however added or incorporated into the filter—enable a filter, a filter component or a specified portion of a filter to be more readily imaged by intravascular ultrasound as described herein. In still another aspect, the characteristics or modification to the filter are oriented and positioned in order to facilitate IVUS imaging via an IVUS probe borne by a filter deployment or retrieval catheter, snare, or other implement provided to facilitate the use of intravascular filters.

FIG. 1 is a section view of a wire strut or support element of a filter (w/s/s) having multiple segments in a concentric arrangement. In this illustrative embodiment, the wire is encased in alternating tube segments. There is an inner tube (IT) directly adjacent to the wire. There is an echogenic segment layer (EL) adjacent to the inner layer. The inner tube may be selected to act as bonding layer to increase adhesion between the echogenic layer and the filter wire, strut or support member. In this embodiment, there is an outer tube (OT) over the echogenic layer. In alternative configurations, either or both of the inner tube or the outer tube may be omitted. The echogenic layer is a segment having one or more of the echogenic characteristics described herein.

FIGS. 2-7 provide various exemplary embodiments of a segment 87 having one or a plurality of one or more than one type of echogenic characteristic, property or feature added thereto. Each of the illustrated echogenic adaptations applied to segment 87 along with segment 87 itself may be sized, scaled and/or shaped as described herein as needed based upon the requirements of the portion of the filter and the echogenic characteristic.

FIG. 2 is an embodiment of a segment 87 having one or a plurality of laser drilled holes 88 formed therein. The diameter and the shape of the holes may be selected based upon the size of the filter or filter component to which the segment 87 will be attached. The holes 88 may be completely through the wall of the segment or only partially through the wall. The holes 88 may be formed in any pattern, spacing or orientation as described herein.

FIG. 3 is an embodiment of a segment 87 having one or a plurality of raised features or alternatively roughed portions 89 formed thereon. The size and shape of the raised features or the roughness of the surface may be selected based upon the size of the filter or filter component to which the segment 87 will be attached. The raised features or portions of roughness 89 may be formed in any pattern, spacing or orientation as described herein.

FIG. 4 is an embodiment of a segment 87 having one or a plurality of bubbles 90 formed therein. The size, shape, pattern, and manner of incorporating one bubble 90 or a plurality of bubbles 90 into the segment 87 may be selected based upon the size of the filter or filter component to which the segment 87 will be attached. The bubbles 90 may be formed within the segment sidewall, near the surface of the segment sidewall or near the inner surface of the sidewall. The bubble or bubbles 90 may be formed in any pattern, spacing or orientation as described herein.

FIG. 5 is an embodiment of a segment 87 having one or a plurality of dimples 91 formed therein. The diameter and the shape of the dimples may be selected based upon the size of the filter or filter component to which the segment 87 will be attached. The dimples 91 may be formed in any pattern, spacing or orientation as described herein.

FIG. 6 is an embodiment of a segment 87 having a coil or braided structure 92 within or about the segment 87. The size, shape, pattern, and manner of incorporating the coil or braid 92 into the segment 87 may be selected based upon the size of the filter or filter component to which the segment 87 will be attached. The coil or braid 92 may be formed within the segment sidewall, near the surface of the segment sidewall or near the inner surface of the sidewall. The coil or braid 92 may be part of a sandwich structure as illustrated and described in FIG. 1. The coil or braid 92 may be formed in any pattern, spacing or orientation as described herein to enhance the echogenic characteristics of the filter or filter portion attached to the segment 87. The coil or braid 92 may be continuous along the entire length of a segment 87 or, alternatively, the coil or braid 92 may be in short lengths selected so that a plurality of coils or braids are provided within a single segment 87.

FIG. 7 is an embodiment of a segment 87 having a plurality of echogenic markers 93 arrayed in rings 93.1, 93.2 and 93.3. For purposes of illustration the rings are shown in an orientation that is generally orthogonal to the central longitudinal axis of the segment 87. The rings are shown with a sample spacing of 1 cm between them. The spacing may be any suitable distance based on the factors described herein such as filter size and physiological environment. Similarly, the rings may be angled in other orientations relative to the longitudinal axis of the segment. For example, some ring may be in one angular orientation while other rings may be in a different angular orientation where the angular orientation or patent of orientation is utilized to provide one or more of the filter functionality or echogenic characteristics described herein. In some specific configurations, the spacing and sizes used are in the millimeter range. In some specific configurations, the spacing and sizes are in the micron range. In some specific configurations, the size and/or spacing of a ring or between adjacent rings are in a combination of mm and micron ranges for sizes, spacings and features. The size and spacing of the echogenic markers 93 may be selected based upon the size of the filter or filter component to which the segment 87 will be attached. The markers 93 may be formed in any pattern, spacing or orientation as described herein in order to facilitate a measurement using the markers. Still further, the markers 93.1, 93.2 and 93.3 may be utilized for provide for other filter characteristics as described herein.

FIG. 8 illustrates various alternative configurations for a segment used alone or in conjunction with other segments. The segments are illustrated along an exemplary wire, strut, or component of a filtering device. The segments may have different characteristics to enable the segment to be more readily imaged by a medical imaging modality used externally, internally or intraluminally. In one aspect, the segment characteristics are selected to provide for imaging enhancements for a filter being used within a vein or an artery. In another aspect, the segments may have different characteristics to enable the segment to be readily imaged by intravascular ultrasound as described herein. In still another aspect, the segments are oriented and positioned in order to facilitate IVUS imaging via an IVUS probe borne by a filter deployment or retrieval catheter, snare, or other implement. In one illustrative embodiment, the segments are selected and arrayed to facilitate imaging utilizing IVUS and an external medical imaging modality. In one exemplary embodiment, the external imaging modality is x-ray.

Also illustrated in FIG. 8 is the use of a combination of different echogenic characteristics (designated E) and radio-opaque characteristics (designated RO). These characteristics may be any of those described herein in any combination. The echogenic characteristic of a segment may be the same as another segment in a grouping such as in the E segments 87.9 and 87.5. Alternatively, the echogenic characteristic of a segment may be different from those in an adjacent group as with segments 87.2, 87.5 and 87.7.

FIG. 8 also illustrates not only that different characteristic and properties of segments may be used but also how variable segment dimensions may be used to aid in echogenic enhancement of a filter. As illustrated, the segments have different widths or thicknesses as indicated along the longitudinal axis of the wire, strut or component. As such, FIG. 8 illustrates a series of imagine enhancing segments 87.1-87.10 having a variety of width or thickness values t1-t10. In one embodiment, the segments are configured as short rings or bands. The thickness of segments in groups may be similar as illustrated in segments 87.1, 87.2 and 87.3 where the thicknesses t1, t2 and t3 are about the same. Similarly, segments 87.4, 87.5 and 87.6 illustrate segments of similar width or thickness where t4, t5 and t6 are about the same value. Similarly, segments 87.8, 87.9 and 87.10 illustrate segments of similar width or thickness where t8, t9 and t10 are about the same value.

FIG. 8 also illustrates how segments within a group or groups of segments may have a variety of different spacing (s1-s6) to provide enhancements to a filter for improving medical imaging modality characteristics. For example, in the segment grouping of 87.1, 87.2 and 87.3, there is a spacing s1 between segment 87.1 and segment 87.2 but then no spacing between segments 87.2 and 87.3. A spacing s2 is shown between segment 87.3 but then no spacing in the combination segment grouping formed by segments 87.4, 87.5 and 87.6. A spacing of s3 is shown between the three segment combination of 87.4, 87.5 and 87.6 to the single segment 87.7. The single segment 87.7 is spaced apart by spacing s4 from the equally sized (i.e., t8=t9=t10) and equally spaced (i.e., s5=s6) group of segments 87.8, 87.9 and 87.10. It is to be appreciated that in various alternative embodiments, the spacing used in groups of segments or between groups of segments may be the same or variable.

FIG. 9 is a view of an exemplary filter illustrating various alternative aspects of providing a filter with improved echogenic characteristics. The filter illustrated is a conical filter. It is to be appreciated that the filter of FIG. 9 is merely representative of one type of filter. It is to be appreciated that the various alternative enhancement, modifications and treatments described herein may be provided to any intravascular or intraluminal filter. The exemplary filter is dividing into three general sections A. B and C. Sections A, B and C may be the same type of enhancement or have an enhancement different from one another section. In addition, the type of enhancement in each section may be the same or different from one another in detection, response or appearance under ultrasound. In addition, a tag, feature or enhancement may be different within a section. Circles 902 are used to indicate exemplary locations for an echogenic feature, tag, marker or modification to an enhanced filter 10. The illustrative embodiment in FIG. 9 also illustrates a continuous echogenic layer, feature or modification or treatment 908. The illustrative embodiment in FIG. 9 also illustrates an echogenic attribute on/near an inflection point 906 in an enhanced filter structure 10. The illustrative embodiment in FIG. 9 also illustrates a segmented echogenic layer, feature or modification or treatment 904 on an enhanced filter structure 10. Section A is considered the apex, tip, distal portion or terminal end depending upon filter configuration. Section B is considered the mid-strut, middle, filtration portion, debris capture portion, or thrombus collection or lysing portion depending upon specific filter configuration. Section C is considered the rear portion, proximal portion, proximal terminal portion, anchor, fixation or perforation portion depending upon a specific filter configuration. It is to be appreciated as well that the echogenic features, tags, markers or modifications illustrated for sections A, B and/or C may be of the same type or different types depending upon the echogenic signature or attribute intended for that section, group or sections or filter. As such, the echogenic features, tags, markers or modifications for a particular section may be selected from any of the various alternatives described herein.

Echogenic characteristics may be added to each of the sections based on the type of function being measured or characterized. For example, echogenic markers, features or tags may be added to Section A in order to provide, for example: identification of the terminal end, end portion or retrieval portion of a filter. Echogenic characteristics of Section A may also be used for determinations related to Section A specifically or the filter generally of filter position, positioning, attitude within the lumen, localization of the filter within the vasculature and other traits common to the characterization of intravascular devices. For example, echogenic markers, features or tags may be added to Section B in order to provide, for example: identification of the mid strut portion, middle or capture region. Echogenic characteristics of Section B may also be used for determinations related to Section B such as for sizing, centering, symmetry of implantation, placement, apposition of implant to vessel walls, clot burden, deployment status or completion, gauge of filter capacity and/or filter contents as well as filter position, positioning, attitude within the lumen, localization of the filter within the vasculature and other traits common to the characterization of intravascular devices. For example, echogenic markers, features or tags may be added to Section C in order to provide, for example: identification of the rear portion, terminal end, retrieval feature, anchor location or depth of insertion, perforation indication or other aspects of the rear or proximal portion of a filter. Echogenic characteristics of Section C may also be used for determinations related to Section C such as for sizing, centering, symmetry of implantation or placement of legs struts and the like, as well as for determination of wall apposition, anchor penetration or perforation. Still further, the markers or tags may be added to aid in determining or evaluating filter position, positioning, attitude within the lumen, localization of the filter within the vasculature and other traits common to the characterization of intravascular devices.

A filter having enhanced echogenic properties is illustrated in FIG. 9 as it appears when it is in operative position within the vasculature. In one specific aspect the filter is in use in a large blood vessel. One exemplary vessel is the vena cava. Still further, a modified filter may be employed in a different vein or even an artery. The filter is designated generally by reference numeral 10, and the wall of the blood vessel in which it is located is designated by reference numeral 12. The filter 10 includes an apical hub 14 of overall egg-shaped or tear drop configuration and which has a generally hemispherically shaped end portion 14 a.

The filter 10 includes a plurality of elongated legs 16 which are of equal length and are identically configured to each other. The legs 16 are collectively arrayed in a conical geometric configuration so that the legs converge to the apical hub 14, and are symmetrically spaced about a central axis extending through the hub. Each of the legs is of equal diameter over its entire length and is made of a relatively resilient material, such as tempered stainless steel wire or the like. In addition to the echogenic attributes described herein, the legs may be coated with a polymeric, synthetic resin material having anti-thrombogenic properties. FIG. 9 illustrates an echogenic marker at the tip 14. Exemplary continuous echogenic layers, features or modifications are also illustrated along one or more legs of the filter. In addition, FIG. 9 illustrates the use of echogenic tags, features or markers at, along or near inflection points in a filter element or component. In addition, FIG. 9 illustrates to application of echogenic markers, tags or features near the fixation elements of the filter.

FIG. 9 is a view of an IVC filter having an improved echogenic characteristic. A filter constructed in accordance with the invention is illustrated in FIG. 9 as it appears when it is in operative position within a large blood vessel, such as the vena cava. The filter is designated generally by reference numeral 10, and the wall of the blood vessel in which it is located is designated by reference numeral 12. FIG. 10 is an end view of the filter in FIG. 9.

The filter 10 includes an apical hub 14 of overall egg-shaped or tear drop configuration and which has a generally hemispherically shaped end portion 14 a. This construction avoids impalement of the filter on the blood vessel walls during emplacement, and also avoids irritation or scratching of the blood vessel during insertion of the filter. The apical hub 14 is drilled for the reception of the end portions of a plurality of legs as hereinafter described.

The filter 10 includes a plurality of elongated legs 16 which are, in some embodiments, of equal length and are identically configured to each other. In one aspect, the legs 16 are collectively arrayed in a conical geometric configuration so that the legs converge to the apical hub 14, and are symmetrically spaced about a central axis extending through the hub. Each of the legs is of equal diameter over its entire length and is made of a relatively resilient material, such as tempered stainless steel wire or the like. The legs may be coated with a polymeric, synthetic resin material having anti-thrombogenic properties. In the embodiment of the filter illustrated, six of the legs 16 are provided, and since each of these legs is identical to every other leg, only one of the legs will be described in greater detail.

At its outer end, or end which is distally located with respect to the apical hub 14, each leg is reversely bent through an angle of more than 90°, and is tapered or sharpened to a point 16 a. The reverse bend is outwardly in a direction away from the central axis of the conical figure. As depicted in FIG. 11, the end portions of the several legs 16 project into bores formed through the apical hub 14, and are secured in the hub by suitable techniques.

It will be seen in FIG. 9 that when the filter 10 is positioned in the blood vessel, the points 16 a at the divergent ends of the legs 16 hook into or impale the wall 12 of the blood vessel, but the hooks are not of sufficient size to penetrate or pass through the wall of the blood vessel. It will further be noted by reference to the arrow within the blood vessel in FIG. 9 that when the blood flows in the direction indicated by the arrow, the pressure exerted by the blood on the filter 10, and any embolus which may be entrapped thereby, tends to set the hooks at the divergent ends of the legs 16 into the wall 12 of the blood vessel so that dislodgment of the filter is resisted.

FIG. 12 is a view of a breakaway anchor portion of an IVC filter having an improved echogenic characteristic. Referring to FIG. 12, an embodiment of the blood clot filtration device 10 of the invention consists of six legs 12 protruding from a head or nosebead 14. The legs 12, e.g., wire of diameter D_(W), about 0.018 inch (0.5 mm), each have: a first linear leg portion 13 lying parallel to axis E of the filter, for distance H_(N), e.g., about 1 mm, a nose bend 15, a second multi angled leg portion 16 of relatively greater length than the first linear leg portion, angling outwardly from the distal end of the first leg portion away from axis E, to define, with other second leg portions, an imaginary cone with base 20, shown as dotted lines; and outwardly directed hooks 22. The second leg portions 16 consist of a series of discrete linear segments arrayed generally tangent to the surface of the imaginary cone in a manner to increase the efficiency of the filtering effect. The diameter of the base of the filter is D_(B), about 38 mm, and the overall length of the filter is L, about 50 mm. The linear leg portions 13 of all of the legs are closely arranged in a hexagonal pattern about central leg stub or segment 24 and the ends of all of these legs are joined at the apex in proximal head or nose bead 14, formed by fusing the ends of legs 12 and central leg stub 24 together.

The wires forming legs 12 are formed into first linear portion 13, second multi angled portion 16 and hook 22 against a steel guide in such a way that there is an alternating bend circumferentially oriented to produce a characteristic conical structure. Hook 22 has length L_(H), about 1.8 mm, and is angled at angle θ_(H), about 34°. The bends 38 in leg wires 12 are formed by bending the wires at an angle of 130°-150°. Hook 22 is formed mechanically by bending the distal end of wire 12 over a mandrel. Hook 22 is then sharpened on three sides against an abrasive wheel. Nose bend 15 is made to form first linear portion 13 near to bead 14, parallel to axis E of filter 10. The leg 12 then bends slightly outwardly on the major angle of the cone and passes through a series of bends as described above.

The embodiment of the filter described above with regard to FIG. 12 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIG. 12 may be modified according to FIGS. 1-9 above.

FIGS. 13 and 14 are of an IVC filters having an improved echogenic characteristic. Referring now to FIG. 13, there is shown a first embodiment of a vena cava filter 10 having an apical hub or head 14 of generally cylindrical shape.

The filter 10 includes a plurality of elongated legs 16 which are of equal length, and are preferably identically configured to each other. The legs 16 are collectively arranged in a generally conical geometric configuration so that the legs 16 converge in the apical head 14, and are symmetrically spaced about a central longitudinally disposed axis “L”, which is shown extending through the head 14, in FIG. 13. The legs are of equivalent diameter, being about 0.018 inches in diameter fabricated from stainless steel or titanium wire, and are of about 2.02 inches in final length. In the embodiment of the present invention, six legs are provided, however only one will be described in detail.

At its outermost end 18 which is distal with respect to the apical head 14, each leg 16 has a main portion 20 and a reversely bent portion 22 which is bent through an angle of about 180° in the plane which is tangential to the conical configuration of the legs, and is disposed parallel and contiguous to the main portion 20. A pointed tip portion 24 of the leg which comprises a hook, extends generally radially outwardly, away from the main portion 20 at an angle of from 70° to about 90°, which tip portion 24 is shown piercing a cava wall 26.

A further embodiment of a vena cava filter 60 is shown in FIG. 14 having an apical head 62. The filter 60 includes a plurality of elongated legs 64 which are of equal length, and are configured identical to each other. The legs 64 are collectively arranged in a slightly outswept but generally conical configuration so that the legs 64 converge in the head 62, and are symmetrically spaced about a central longitudinally disposed axis “L”, which is shown extending through the head 62 in FIG. 13. The legs are about 0.018 inches in diameter fabricated preferably from stainless steel, only one of the legs being described in detail. Each leg has an outermost or distal end 66 with a hook configuration disposed thereon.

A typical leg 64 is each mounted in a bore 68 in the apical head 62, which bore may be parallel to the center line of the filter 60. Each bore 68 receives only about 0.19 inches of the proximalmost end of each leg 64. When all the legs 64 are filling their proper respective bores 68, they are preferably welded therein. Each leg 64, in addition to having a plurality of U-shaped bends 70, disposed in the plane tangential to the cone defined by the legs 64, and intermediate their proximal and distal ends, as recited in the aforementioned incorporated patent, has a first slight bend 72 having a radius of curvature RI of about 1.4 inches arranged immediately adjacent the apical head 62, to cause the leg(s) 64 to flare radially outwardly about 18 degrees, thus defining their cone shaped configuration. This flare permits the filter 60 to have enough elastic recoil to assume its general conical configuration, which is desirable to permit the filtration of blood clots while still allowing blood to flow around the captured clots, thus promoting dissolution of any clot and maintenance of vessel patency. The filter 60 with this flare can be passed through small delivery carriers without exceeding the elastic limit of the stainless steel filter legs 64.

The apical head 62 on the filter 60 has a central cylindrically shaped bore 80 which is adapted to receive inself aligning engagement, a guidewire (not shown). The bore 80 critically has its cylindrical portion which is in axial alignment with the longitudinal center line “L” of the filter 60. Each end of the bore 80 has a tapered counterbore 82 to permit access of a guidewire into the bore 82. This permits the filter 60 to be aligned and centered along the axis of a guidewire in a vessel during (and after) filter emplacement therein.

The embodiment of the filter described above with regard to FIGS. 13 and 14 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIGS. 13 and 14 may be modified according to FIGS. 1-9 above.

FIG. 15 is a view of an IVC filter having an improved echogenic characteristic. FIG. 15 is a perspective view of a thrombus filter 20. Thrombus filter 20 includes a body member 22 and a plurality of elongated struts 24. Struts 24 each have a joined end 26 and a free end 28. Joined end 26 of each strut 24 is fixedly attached to body member 22.

Struts 24 may be fabricated from wire with a circular or rectangular cross section. For example, struts 24 may be comprised of 2 inch lengths of 0.018″ diameter wire. Stainless steel, titanium, and nickel-titanium alloys have all been found to be acceptable materials for struts 24. In the embodiment of FIG. 15, a plurality of bends 25 are disposed between free end 28 and fixed end 26 of each strut 24. It should understood that struts 24 may also be straight, or include bends different than those illustrated in FIG. 15, without departing from the spirit of scope of the present invention.

In the embodiment of FIG. 15, body member 22 is generally cylindrical in shape, and includes a bore 23. It should be under stood that other embodiments of body member 22 are possible without departing from the spirit or scope of the present invention.

Struts 24 radiate outwardly from body member 22 such that thrombus filter 20 is generally conical in shape. When thrombus filter 20 is deployed inside a blood vessel, free ends 28 engage the blood vessel wall. Body member 22 is held in a position proximate the center of the blood vessel by the plurality of struts 24 which engage the blood vessel walls with opposing force vectors.

When thrombus filter 20 is disposed in a blood vessel, the conical formation of struts 24 acts to trap, or capture blood clots. The generally conical shape of the formation of struts 24 serves to urge captured blood clots toward the center of the blood flow. The flow of blood around the captured blood clots allows the body's natural lysing process to dissolve the clots.

To assure firm attachment of thrombus filter 20 to the blood vessel walls, anchor portions 30 may be formed at free ends 28 of struts 24. FIG. 16 illustrates one embodiment of an anchor portion 30 embedded in a vessel wall 32. Anchor portion 30 includes a sharp point 34 and a bend 36. Strut 24 includes a weakened portion 40 disposed proximate free end 28. In the particular embodiment of FIG. 16 weakened portion 40 includes a plurality of divets 42. Divets 42 substantially reduce the cross sectional area of strut 24 at weakened portion 40. Divets 42 may be fabricated by removing material from strut 24 with a removal process such as machining or grinding. Divets 42 may also be fabricated by displacing material with a process such as metal forming or crimping.

Blood vessel wall 32 is lined with a thin inner membrane or intima 44. When anchor portion 30 is embedded in wall 32 it punctures inner membrane 44. The body responds to a puncture of inner membrane 44 with a process known in the art as neointimal hyperplasia. The punctured area of inner membrane 44 is overgrown with a number of new cells. Referring again to FIG. 16, it can be seen that anchor portion 30 of strut 24 is covered with encapsulating cell growth 46.

It is desirable that the thrombus filter of the present invention can be removed using minimally invasive methods without complications due to neointimal hyperplasia encapsulation of anchor portions 30 of struts 24. A process which may be utilized to remove thrombus filter 20 from a blood vessel 90 is schematically represented in FIG. 17.

FIG. 17 schematically illustrates a blood vessel 90 including a lumen 92 and walls 32. Thrombus filter 20 is disposed in lumen 92 of blood vessel 90. Anchor portions 30 of struts 24 are embedded in walls 32 of blood vessel 90. Neointimal hyperplasia has resulted in encapsulating cell growth 46 proximate anchor portions 30 of struts 24.

A removal catheter 100 with a lumen 102 and a distal end 104 is also disposed in lumen 92 of blood vessel 90. Removal catheter 100 enters the patient's vascular system at a point which is readily accessible to the physician. Once in the vascular system, catheter 100 is urged forward until distal end 104 is proximate thrombus filter 20. For example, if thrombus filter 20 is located in the inferior vena cava of a patient's vascular system, removal catheter 100 may enter the vascular system at the femoral vein. Alternately, if thrombus filter 20 is located in the superior vena cava of a patient's vascular system, removal catheter 100 may enter the vascular system at the jugular vein. In either case, the filter removal procedure can be minimally invasive, and not require general anesthesia.

Distal end 104 of removal catheter 100 is urged forward so that body member 22 of thrombus filter 20 is disposed inside lumen 102 of removal catheter 100. A force F is applied to thrombus filter 20 urging body member 22 further into lumen 102 of removal catheter 100. The magnitude of force F is of sufficient magnitude to break struts 24 at weakened portions 40. When struts 24 are broken at weakened portions 40 thrombus filter 20 including struts 24 may be pulled into lumen 102 of removal catheter 100. Removal catheter 100 may then be removed from the body of the patient by withdrawing removal catheter 100 from blood vessel 90. Thus, thrombus filter 20 is removed from blood vessel 100 but anchor members 30 remain attached to walls 32 by encapsulating cell growth 46.

FIG. 18 is a schematic representation of thrombus filter 20 after it has been pulled into lumen 112 of retrieval catheter 110. As may be seen in FIG. 18, pulling thrombus filter 20 into lumen 112 of retrieval catheter 110 causes struts 24 to collapse. When struts 24 are collapsed, retrieval catheter 110 may be withdrawn from blood vessel 100. As can also be seen in FIG. 18, anchor members 30 remain fixed in the walls of blood vessel 100, retained by encapsulating cell growth 46.

Force F may be applied to thrombus filter 20 using a variety of methods. For example, the pulling of thrombus filter 20 into lumen 112 of retrieval catheter 110 may be accomplished with a retrieval wire including a hook. The retrieval wire may pass through bore 23 of body member 22. With the retrieval wire disposed in bore 23 of body member 22, the hook may engage body member 22 so that a pull force can be applied to thrombus filter 20.

Struts 24 may also be intentionally broken at weakened portions 40 by repeatedly deflecting struts 24 to induce fatigue cracking at weakened portions 40. The magnitude of the force required for this removal method is less than the magnitude of force required to break struts 24 without fatigue cracking.

A number of methods may be used to deflect struts 24. First, a pull force may be applied to thrombus filter 10 as shown in FIG. 17. Applying a pull force to thrombus filter 20 deflects blood vessel walls 32 and struts 24. When the pull force is released, blood vessel walls 32 and struts 24 deflect a second time in returning to an unstressed position. Pulling force F may be applied and released repeatedly to induce fatigue cracking at weakened areas 40. It should be noted that the pull force applied when using this removal method is not sufficient to break struts 24 at the outset. However, multiple applications of force F cause fatigue cracks to grow at weakened areas 40. As described above the cross-sectional area of struts 24 is reduced at weakened areas 40 by slots, holes, and the like. The cross-sectional area of struts 24 is further reduced by fatigue cracking due to repeated applications of force F. After multiple applications of force F, the cross-sectional area of struts 24 at weakened areas 40 will be small enough that force F alone is sufficient to break struts 24 at weakened areas 40.

The embodiment of the filters described above with regard to FIGS. 15-18 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIGS. 15-18 may be modified according to FIGS. 1-9 above.

FIG. 19 is a view of an IVC filter having an improved echogenic characteristic. FIGS. 19 and 20 show a blood clot filter of the clot filter assembly designated at 10. Filter 10 is shown in a totally straightened position in FIG. 19 with its wire strands slightly spaced apart so that the construction of filter 10 may be more clearly seen. FIG. 20 shows filter 10 in a partially straightened but also somewhat curled position. It should be understood that filter 10 would normally assume the shape of a curly wire mesh unless external forces are employed to straighten the wire strands. It is also to be understood that filter 10 would be provided to the physician in a prepackaged assembly additionally including a cartridge catheter and a wire guide handle, both of which will be more fully described herein.

Filter 10 includes six strands of stainless steel wire which are connected to each other in the following manner. Innermost strands 11 and 12 are mutually attached at both ends by crimps 13 and 14. Innermost strands 11 and 12 are approximately 25 centimeters in length and are made from 0.007 inch diameter coil wire. Outermost strands 15 and 16 are located oppositely of innermost strands 11 and 12 and are each connected thereto at both ends by wire strands 17 and 18. Outermost strands 15 and 16 are approximately 38 centimeters in length and are made from 0.007 inch diameter coil wire. Wire strand 17 serves to connect outermost strands 15 and 16 with innermost strands 11 and 12 at the distal end of filter 10. In a similar manner, wire strand 18 connects outermost strands 15 and 16 with innermost strands 11 and 12 at the proximal end of filter 10. Wire strand 17 is secured to outermost strands 15 and 16 by crimps 21 and 22, respectively and to innermost strands 11 and 12 by crimp 13. In a similar fashion, wire strand 18 is secured to outermost strands 15 and 16 by crimps 19 and 20, respectively, and to innermost strands 11 and 12 by crimp 14. Wire strands 17 and 18 are approximately 10 centimeters in length and are made from 0.010 inch diameter stainless steel coil wire. Crimps 19-22 are made from 3 mm, of 22 GTW cannula while crimps 13 and 14 are made from 3 mm, lengths of 19.5 GTW cannula. Innermost strands 11 and 12, and outermost strands 15 and 16 are made from a shape memory material, such as spring temper stainless steel.

During manufacture, wire strands 11, 12, 15 and 16 are curled in different directions and wadded together to form a curly wire mesh. Because of their shaped memory construction, innermost strands 11 and 12 and outermost strands 15 and 16 may be straightened out at their ends substantially as shown in FIG. 19 for loading into the lumen of a Teflon angiography catheter cartridge. It may be noted that once loaded within the catheter, the spring bias inherent within the wire strands will cause some curling thereof. Further curling is, of course, restrained by the intimal wall of the catheter cartridge. Thus, it is the spring bias inherent in the shape memory construction which allows filter 10 to expand radially outward as innermost wire strands 11 and 12 and outermost wire strands 15 and 16 contract along their lengths upon insertion in a body blood vessel, as will be more fully explained herein.

Anchoring filter 10 within a body blood vessel, such as the inferior vena cava, is generally provided by fixation elements at 24 and 25, the details of their construction being more clearly understood by reference to FIG. 20. It is to be understood that anchor 24 is located at the rearward end of both wire strands 15 and 16, while anchor 25 is located at the forward end of both wire strands 15 and 16. Anchor 24 differs from anchor 25 due to the presence of a barb 30 whose purpose will become fully apparent hereinafter. The anchor 24 and 25 at the ends of outermost wire strand 15 are longitudinally staggered from the corresponding anchor 24 and 25 at the ends of outermost wire strand 16. This permits the easy loading of filter 10 within the lumen of a catheter cartridge such as will be more fully described herein.

Referring particularly to FIG. 20, the details of construction of the rearward anchoring means 24 will now be described. It is to be understood that while only the rearward anchor 24 at the end of outermost wire strand 15 is described, the rearward anchor means 24 at the end of outermost wire strand 16 is of a similar construction. It is seen that rearward anchor means 24 includes a length 26 of outermost wire strand 15 located at the rearward end thereof. Length 26 is approximately one centimeter in length and has a sharp end point 27 which is meant to enter the wall of a blood vessel. In order to prevent too deep penetration of anchor 24 through the blood vessel, a loop 28 of wire formed from wire strand 18 is positioned adjacent length 26. Loop 28 extends approximately 7 mm along length 26, crimp 19 serving to secure the end of loop 28.

It is to be understood that there are two forward anchor 25 at the forward end of filter 10. As previously mentioned, forward anchor 25 is of a similar construction to anchor 24 except that a barb 30 is received over the end length of wire corresponding to length 26 of anchor 24. The purpose of barb 30 is to provide a more secure anchor at the downstream end of filter 10 and thereby ensure long term patency of the filter. Barbs 30 are secured to the forward ends of the outer most wire strands 15 and 16 by soldering. Each of the barbs 30 have a lancet beveled portion 31 which faces outwards of filter 10 and a hooked portion 32 at the inwards facing end. Hooked portion 32 serves to prevent barb 30 from becoming dislodged from the body blood vessel once penetration thereof has been made. Each of the barbs 30 is constructed from 6 mm, to 0.028 inch diameter cannula.

FIG. 21 show filter 10 in its longitudinally contracted and radially expanded position within the inferior vena cava of a human body. It is to be noted that in this position filter 10 is in the shape of a curly wire mesh with spaces therethrough no larger than 3-4 mm. Also, due to the relatively small diameters of the wire strands, filter 10 occupies only a minimal portion of the cross-sectional area of the blood vessel passageway. Thus, filter 10 does not substantially occlude the blood vessel passageway. Also, barbs 30 extend into the intimal wall of the inferior vena cava in such fashion so as to firmly anchor filter 10, thereby ensuring long term patency.

In addition to the anchoring points at barbs 30, FIG. 21 also shows filter 10 in urging contact with the intimal wall 70 of the inferior vena cava 65 at innumerable other points along the lengths of various portions of the wire strands of filter 10. Initially, these points of urging contact do not provide sufficient anchoring to ensure patency of filter 10, thus requiring the anchoring provided by barbs 30. However, after several weeks endothelization and fibrotic encasement occurs at the points where the wire mesh of filter 10 abuts the intimal wall of the inferior vena cava, and the likelihood of permanent patency is thereafter greatly increased.

FIG. 22 is an alternative embodiment similar to FIG. 20. FIG. 22 includes 2 V-shaped struts supporting the fine wires as described above.

The embodiment of the filter described above with regard to FIGS. 19-22 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIGS. 19-22 may be modified according to FIGS. 1-9 above.

FIG. 23 is a view of an IVC filter having an improved echogenic characteristic. The filter 10 in FIG. 23 is made up of a set of seven wires. Six of these are approximately three inches in length when fully extended. The seventh is approximately two inches in length when fully extended. The wires are held together by two small sleeves or coils 12 and 14 of the same material, each coil being spot welded to hold it in place and approximately one-quarter of an inch in length; coil 12 is adjacent the tip 13 of the seven wires, and coil 14 is approximately two inches from tip 13 when the wires are fully extended. In the low temperature phase of the material the set of wires can be straightened and held in a straight form that can pass through a length of fine plastic tubing with an internal diameter of approximately 2 mm (#8 French catheter).

In its normal expanded configuration or performed filtering shape, filter 10 is a double filter, having a first filter basket 16 and a second filter basket 18. The two filter baskets provide peripheral portions which engage the inner wall of the vein at two longitudinally spaced locations. The two filter baskets are generally symmetrical about a longitudinal axis passing through filter tip 13.

The mesh of first filter basket 16 is formed from the sections of wires between the two quarter-inch coils 12 and 14. The mesh is made up of a series of seven overlapping loops 20 arranged to form a rosette approximately 25 mm in diameter. The loops are angled slightly relative to the long axis of filter 10 and this angle can be varied to accommodate somewhat smaller diameters if the device is to be constrained in a tube of less than 25 mm in caliber. The loops 20 effectively divide the cross-sectional area to be filtered. The rosette formed by loops 20 can expand or be compressed to fit various sizes of vein. The peripheral portions or tips of the loops 20 press outwardly against the inner wall of the vein, although without becoming imbedded in the vein; loops 20 thereby help to keep filter 10 in place. First filter basket 16 is convex relative to filter tip 13.

The mesh of second filter basket 18 is formed by the six circumferentially spaced free wire ends or legs 22, which tilt and bow outwardly of the long axis of filter 10. The seventh wire terminates within sleeve 14 for use in inserting filter 20. The six free ends or legs 22 that extend beyond the second quarter inch coil 14 diverge so that their tips form a circle 24 of approximately 40 mm in diameter at their maximum divergence. Each leg is also bowed outwardly slightly. The legs serve to orient the device relative to the long axis of the vena cava. Second filter basket 18 is convex relative to filter tip 13.

In another alternative embodiment the legs are tilted outwardly but are not formed with a bow. In such an embodiment, second filter basket 18 opens away from filter tip 13 without being strictly convex.

Each free end of leg 22 is bent sharply outward at about a right angle to form a hook 26 of approximately 1.5 mm in length. The hooks are intended to engage the wall of the vena cava to prevent migration proximally or distally.

The six legs 22 are of slightly different lengths to permit good packing within the delivery device, as will be described; if legs 22 are all of a single length, the hooks may interfere with one another, so that the filter does not expand properly when delivered into the vein.

FIG. 24 is a view of an IVC filter having an improved echogenic characteristic. In FIG. 16, a blood clot filter of the type intended for percutaneous introduction and delivery using a transfemoral approach is shown and is designated generally by reference numeral 20. Within FIG. 16, dashed lines 22 and 24 indicate the outline of an interior wall of a blood vessel, such as the inferior vena cava. Blood clot filter 20 consists essentially of a central core wire 26 which extends generally along the central longitudinal axis of blood clot filter 20, as well as six peripheral wires 28, 30, 32, 34, 36 and 38 spaced equiangularly about central core wire 26. Peripheral wires 36 and 38 are hidden from view in FIG. 16 by peripheral wires 30 and 32, respectively.

In FIG. 24, a first connector 40 is shown forming a nose of blood clot filter 20. Connector 40 serves to connect together a first end of each of peripheral wires 28-38, and attaches such peripheral wires about the first end of central core wire 26 at a first connection point. Connector 40 is welded, crimped or otherwise attached to the first end of central core wire 26 and to the first ends of peripheral wires 28-38 so that a fixed connection is achieved between the central core wire and the six peripheral wires.

Still referring to FIG. 24, the six peripheral wires 28-38 are again joined along their central portions by a second connector 42. Connector 42 is in the form of a tubular collar having a central opening defining an interior wall 44. Each of the peripheral wires 28-38 passes through tubular collar 42 and is secured to interior wall 44 thereof, as by welding or by other means of attachment. Thus, second connector 42 serves to connect together peripheral wires 28-38 at a second connection point spaced apart from the first connection point at first connector 40, it will be noted that central core wire 26 passes freely through the interior space defined by tubular collar 42 and the peripheral wire secured therein, thereby allowing second connector 42 to slide along central core wire 26.

The embodiment of the filter described above with regard to FIGS. 23 and 24 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIGS. 23 and 24 may be modified according to FIGS. 1-9 above.

FIG. 25 is a view of an IVC filter having an improved echogenic characteristic. The filter in FIG. 25 comprises four legs 1, 2, 3 and 4 diverging from an apical hub 5 at which the legs 1 to 4 are held together by an end ferrule 6 of the kind e.g. disclosed in U.S. Pat. No. 4,619,246, incorporated herein by reference.

Each leg comprises a central element 1 a, 2 a, 3 a, and 4 a bent into a smooth quasi-halfsinusoidal form and having a reversely turned anchoring hook 1 b, 2 b, 3 b and 4 b at its distal end with respect to hub 5 as well as two symmetrical curved side elements 1 c, 2 c, 3 c and 4 c, and 1 d, 2 d, 3 d and 4 d extending on either side of the central element.

In the embodiment shown the two side elements of each leg 1 to 4 are formed from one piece of wire the ends of which are held together in hub 5, whereas at the middle of its length the wire piece forms an eyelet 7, 8, 9 and 10 surrounding the central leg element to be freely slidable along a part of the length thereof.

From the unfolded tulip-like configuration illustrated in FIG. 25 the filter may be collapsed into a slender and very narrow bundle of filter elements the cross-sectional dimension of which is approximately equal to the sum of the thicknesses of the central and side elements of all four legs.

The side elements of each leg have a length and curvature such that in the unfolded tulip-like configuration of the filter the maximum distance between the side elements is of the same order as the distance between neighboring side elements of two adjacent legs. Moreover, the length and curvature is preferably chosen such that after insertion into the vena cava inferior the eyelets 7-10 will be positioned substantially at the inner side of the wall of the blood vessel.

As best seen in FIG. 25 the filter according to the invention has in its unfolded state a relatively short axial length of the same order as the diameter of the filter whereby proper arrangements of the filter into the inferior vena cava is facilitated.

The embodiment of the filter described above with regard to FIG. 25 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIG. 25 may be modified according to FIGS. 1-9 above.

FIG. 26 shows a filter generally designated by the numeral 12, and in FIG. 27 it is seen to comprise a generally dome-shaped body 14 of open work construction composed of skeletal members such as 16, 18, 20, 22, 24 and 26 which are arranged in a manner somewhat similar to the struts of an open umbrella canopy, and when in the open position shown in FIG. 27, span a distance d greater than that which characterizes the range of diameters commonly encountered in the inferior vena cava. In the preferred embodiment, the six radiating spokes are of collapsible, resilient, alloy material. The inward or converging proximal ends of the spokes or frame members con-verge to a hub 28 and are there united forming the skeletal frame. The distal ends of the struts or spokes all extend somewhat beyond the outer lip or margin of the canopy now to be described, and these ends are preferably sharpened to comprise a holding and gripping means, as will be apparent hereinafter. The canopy portion 30 comprises a suitable filter media of generally sheet form overlaying and being supported on the framework. Preferably, the filtering media includes a plurality of holes in the preferred embodiment, one hole being disposed in the generally triangular portion of the canopy between each of the spokes, and these holes or openings, one of which is designated by the numeral 32 for purposes of clarity, are on the order of about 3 millimeters in diameter and are circular in cross section. The pointed distal ends of the spokes appear as circumferential teeth which extend outwardly of the canopy. The hood or canopy is preferably of a flexible, smooth surfaced material, such as a plastic material, and which provides a smooth surface. For purposes-which will be apparent hereinafter, there is an axial recess 50 in the hub which is threaded.

The embodiment of the filter described above with regard to FIGS. 26 and 27 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIGS. 26 and 27 may be modified according to FIGS. 1-9 above.

With reference firstly to FIG. 28, there is thus illustrated a filter 1 in the unfolded position consisting of fingers 2, of which there are ten for example, which emerge from a head 3 and which can be unfolded substantially in a generally conical shape of which the opening is marked in dashed lines at 4. Each finger is provided at its free end with a centering and bearing runner 5 which turns substantially behind the head 3; that is, this runner 5 is directed from the end 2 a of the fingers towards the closure side of the cone forming the filter. More precisely, if we designate as 6 the cylinder generated by a generating line that is parallel with the axis 7 of the conical shape formed by the filter 1 and moved such that it describes the line 4, the runners 5 are directed such that they are substantially parallel with the wall of the cylinder 6.

In accordance with the invention, the filter fingers consist of flexible wires 8. They may in particular consist of metal wires, for example of a suitable grade of stainless steel. The diameter of the wires may be between 2 and 4 tenths of a millimeter for example 3 or 3.5 tenths of a millimeter.

These fingers are combined in groups of two adjacent fingers by a wire part which is folded in the manner of a hairpin 9 and forms said runners. As a result, the fingers are in the general shape of a clip 10. Advantageously, the filter preferably comprises at least six of the above fingers connected to three wire portions folded in the manner of a pin and distributed in an angular manner so as to ensure that the filter has good axial stability.

Referring to FIG. 29, it will be noted that the filter, which is generally indicated 1, comprises a series of elongated branches or legs 3 each of which is substantially “V”-shaped. One of the free ends of each “V” comprises fixation means such as a hook 5 for anchoring the filter to the vessel wall. The other end is connected to a metal thread, which has a succession of corrugations or undulations (such as zig-zags) forming a resilient annular structure 7 of which the central opening has a diameter which can be more or less “constricted” and which is adapted to permit the passage of the temporary filter. The various branches 3 can be produced in the form of fine metal threads and are secured around the annular structure or ring 7 However, the whole of the filter could also be produced in a single metal piece, its structure being obtained by cutting.

In order to be introduced into the vessel, the filter 1 can adopt a constrained state in which the elongated branches or legs 3 are moved close up to the axis 18 of the central opening of the filter until they are substantially parallel thereto. When it is in place in the vessel, the filter adopts a radially expanded state, the branches 3 then moving away from the axis 18 and the hooks 5 anchoring themselves in the vessel wall.

The embodiment of the filter described above with regard to FIGS. 28 and 29 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIGS. 28 and 29 may be modified according to FIGS. 1-9 above.

In FIG. 30 there is illustrated a vena cava filter comprising a filter basket generally designated by 1 and consisting of a plurality of thin resilient wires 2 of a suitable material, preferably a stainless steel alloy. As illustrated in FIG. 30, basket 1 is generally shaped as an elongate, apertured solid of revolution resulting from the rotation of a sinusoid curve about an axis of rotation indicated in FIG. 30 by a dot-and-dash-line 3, which is tangent to the generatrix at the ends thereof. At each end of the basket proper, the wires are interconnected by means of a short ferrule 4 secured to the wires by any appropriate means, such as brazing.

As shown in FIG. 30 the ratio of the basket length to its maximum diameter is approximately 2. It should be understood that the exact value of this ratio is not critical for the function of the filter basket and in practice it may assume a value between 1.5 and 3, or even higher, although probably the improvement at higher values may be marginal.

As appears from FIG. 30, between the end ferrules 4 each wire 2 follows a helix-like curve, all curves being similar and having the same “hand”, in the example right-handed. From one end to the other, each wire 2 is “twisted” approximately 90° about the axis 3.

In FIG. 30 a small, oblong eyelet 5 of wire similar to wires 2 is secured in each ferrule 4 so as to protrude axially from basket 1. By means of either eyelet 5 and a mating hook or other gripping device at the end of an insertion wire, the collapsed filter basket may be pushed or pulled through an inserting catheter, as briefly discussed above.

A plurality of anchoring legs 6, in the example five, are secured in the right-hand ferrule 4 of FIG. 30, from which they extend axially away from basket 1 and outwardly relative to axis 3. The free end of each leg 6 is bent outwardly to form a hook 7 which, when the filter basket has been positioned in a blood vessel, penetrates slightly into the wall of the vessel so as to hold the filter basket in position. Legs 6 will normally be made of the same or a similar material as wires 2 so that they can be readily collapsed to fit within the lumen of the insertion catheter, and spring back to engage the wall of the blood vessel when released from the catheter. The pronounced S-shape of legs 6 in the region immediately inwardly of hooks 7 ensures that when the filter basket moves through the catheter it will be the smooth curved portions of the legs rather than the hooks 7 which contact the catheter wall.

The embodiment of the filter described above with regard to FIG. 30 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIG. 30 may be modified according to FIGS. 1-9 above.

Referring now to the drawings, FIG. 31 shows the filter 1 of the present invention which firstly comprises filtering section 2 adapted to open out in the blood vessel 3, particularly the inferior vena cava, when the filter is correctly positioned in the patient.

These filtering section 2 are advantageously constituted by an assembly of flexible filiform elements 4 joined together by one of their ends to form substantially the envelope of a cone, ogive or the like.

In this way, this assembly of filiform filtering elements 4 will be permeable to the blood flow, indicated by arrows 5, but adapted to retain the clots. To that end, it will be disposed in the direction of the blood flow, i.e. the apex of the cone or the like will be directed substantially in the same direction as the blood flow.

By way of example, the flexible rods 4 will be six in number and made of a biocompatible material, such as a suitable metal alloy or plastics material. However, these materials will be chosen for their aptitude to elasticity and to deformation.

In fact, the rods 4 will represent a good flexibility in order, on the one hand, to be folded in a catheter of small dimensions and, on the other hand, to open out correctly in the blood vessel to form a barrage at the latter's dimensions.

Furthermore, the filiform filtering elements 4 will be such that they are non-aggressive with respect to the inner walls of the vessel.

More precisely, as shown in FIG. 31, the rods 4 present at least a slight angle or curve 6, so that their terminal part 7 is in non-aggressive contact with the vessel, when the filtering means are opened out, but so that there is no penetration of the ends of the rods 4 in the wall of the vessel proper.

The embodiment of the filter described above with regard to FIG. 23 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIG. 23 may be modified according to FIGS. 1-9 above.

Referring now to the drawings, and firstly to FIG. 32, a filter device (hereinafter referred to as “filter”) according to the present invention is essentially constituted by an assembly of identical, curved, elastic legs 1, for example six in number, disposed in two's successively in opposite direction, and joined together at their ends 2, 3, particularly by fixing them, for example by electrical spot welding, on two connecting pieces 4, 5.

Each connecting piece is constituted by a substantially cylindrical, hollow piece, the connecting pieces 4 and 5 presenting different internal diameters.

Legs 1, in the out-spread state for use, are angularly distributed in substantially regular manner, for example spaced apart successively in two's by about 60°.

Each leg 1 comprises a convex portion, whose apex 6 is adapted to abut against the inner wall of the vein 7 when the legs are in out-spread state for use.

This convex portion, which may for example be made by burnishing, is closer to one end of leg 1 than the other, with the result that, the legs being identical and mounted successively in two's in opposite direction, said filter abuts on the vein, at the level of apices 6, via two series of points spaced apart longitudinally by a predetermined distance.

The embodiment of the filter described above with regard to FIG. 32 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIG. 32 may be modified according to FIGS. 1-9 above.

As shown in FIG. 33, the embolus trap comprises a central cylindrical column 11 to which is attached a plurality of upper elongated loops 12 of filaments 13 and 14, such as metal wire, and a plurality of like lower loops 15. Loops 12 and 15 are assembled in two tiers spaced from one another on column 11. The loops 12 in the upper tier are circumferentially spaced from each other in symmetrical fashion, as are the loops 15 in the lower tier. The loops of adjacent tiers are displaced from each other circumferentially, preferably centrally, so that a loop 12 of the upper tier is centrally located between two loops 15 of the lower tier, and vice versa. The inner ends of adjoining filaments, such as 13 and 14, are anchored in central column 11 and the outer ends of those filaments are joined or abutted to form a closed elongated loop. The outer ends of filaments 13 and 14 are bent toward each other to form short circumferentially extending portions 18 and 19 respectively, and then 180° in the same plane to form oppositely extending circumferential portions 20 and 21 respectively. The extreme ends of portions 20 and 21 are bent radially outwardly into hooks 22. The wires of each loop may be joined at the crowns of the open loops formed by bent portions 18 and 20 of wire 13 and 19 and 21 of wire 14, as by tying the wires over the loops. Those circumferentially bent portions 20 and 21 form a stop or barrier which prevents hooks 22 from penetrating the wall 24 of the passageway 10 sufficient to puncture it.

As shown in FIG. 33, The filaments in each tier are positioned in pairs at the desired spacing around column 11, enclosed in a metal sleeve 50, and are welded thereto at an end of the sleeve. The sleeve 50 with filaments attached is then crimped on column 11. Column 11 is hollow, and preferably rigid, having a central cavity 51 running therethrough.

The embodiment of the filter described above with regard to FIG. 33 may be modified to be a filter having enhanced echogenic properties characteristics or features. This filter embodiment may be modified with enhanced echogenic characteristics including one or more than one of: (a) a modification to one or more components of the filter to enhance the echogenic characteristics of the component; (b) formation of dimples into a component surface of sufficient number and scaled to a suitable size, shape, orientation and pattern for use with intravascular ultrasound systems; (c) protrusions formed in, placed on or joined to a filter surface; (d) roughening one or more surfaces of a filter, for example using a chemical process, a laser or bead blasting technique; and (e) altering one or more steps of a filter manufacturing technique to introduce cavities, voids or pockets to locally modify or adapt one or more acoustic reflection characteristics to improve echogenicity in one or more specific regions of a filter. In other aspects, the filter illustrated and described in FIG. 33 may be modified according to FIGS. 1-9 above.

In some aspects, any of the above described filters may be modified to include hybrid or dual mode features. One example of a dual mode feature is one that is both radio opaque and also echogenic. In still another aspect, the above described filters may also include a material capture structure as described below, with or without one or more imaging modes as described herein.

In still other alternative embodiments, there is provided a material capture structure having one or more echogenic enhancements alone or in combination with radiopaque enhancements. In one aspect, the filter structure used in a filter includes both echogenic and radio opaque enhancements.

An one aspect, the filter includes material capture structure in the IVC filter will be viewable under fluoroscopic and ultrasound imaging modalities, including appropriate echogenic characteristics to enhance the view of the status or condition of the material capture structure while using IVUS. Enabling the material capture structure to be viewed will allow the physician to appropriately center and verify placement of a filter.

In one aspect, the filter elements or structures are doped to incorporate one or more of echogenic or radio opaque materials or treatments. In one aspect, the filaments or strands or other structures used to form the filter structure or webbing of the filter includes a radiopaque material having high echogenic properties, such as tungsten or gold, but not limited to either.

In other embodiments, one or more filaments or portions of a filament within a material capture structure includes one or more non-metallic echogenic features, such as those described elsewhere in this specification. For example, a filament or portion thereof may include air pockets either added to the material or by the use of materials with entrained air or gas that are used. In one embodiment, an ePTFE suture has echogenic properties due to air content of the ePTFE material. In other aspects, a suture material or a filament or polymer strand may also include dimpled/roughened/matrix/sponge materials, additives, or modifications to provide or enhance the overall echogenic nature of the suture, filament, material or material capture structure, in whole or in part.

In one aspect, these additional materials may assist the physician in centering or placing a filter within a vessel. In another aspect, this improvement is used in conjunction with IVUS will enable the adequate viewing of the filter portion of the filter and will allow for co-registration of filter placement along with an accurate entry/removal of the catheter through the webbing of the filter.

The advantages of this inventive aspect of a filter include, for example and not limitation, filter placement, accurate representation of filter location, ease of introducing/retracting catheter, more viewable space for more accurate assessments, ability to co-register filter location with IVUS and/or ability to better place filter in desired location.

Still other aspects of the use of the innovative filter include, for example, deployment of filters, positioning of filters, sizing of filters, and estimated treatment lengths as well as suture and/or material capture structure visibility. In still other aspects of the use of the innovative filter include, for example, deployment of a vena cava filter, positioning of an IVC filter, sizing of an IVC filter, and estimated treatment lengths as well as enhanced suture visibility.

In one embodiment, there is an IVC filter delivery system with an enclosed IVC filter. This filter would have a mesh, suture, web or other material capture structure suited to the anticipated filter use. The mesh, suture, web or other material capture structure has one or more components that is doped with a highly radiopaque material for better visibility under flouro and good echogenicity for better viewing under IVUS guidance. In still further alternative embodiments, the techniques described above may be applied to one or more material capture structure described in U.S. Patent Application Publication No. US 2008/0147111 entitled “Endoluminal Filter with Fixation” filed Jun. 4, 2008 as U.S. patent application Ser. No. 11/969,827, (the “'7111 publication”) incorporated herein by reference in its entirety for all purposes. More particularly, the aspects of modifying a material capture structure to exhibit radio opaque, echogenic of combinations of radio opaque and echogenic characteristics may be applied to the various embodiments illustrated and described in FIGS. 30-34B, 38A-38B, 39-67, and 83-87. In one particular aspect, the filament/strand/suture 461 shown in FIG. 58 of the '7111 publication may be coated or doped as described above alone or in combination with the illustrated pharmacological coating 466.

In still another alternative aspect, any of the material capture structures in the '7111 publication may be combined with any of the filters illustrated and described in FIGS. 9-33. The material capture structures may be joined to the wires or other supports in the filters described herein to provide additional kinds of filtering capabilities in addition to or in place of the filtering capabilities of the filter so described.

In some embodiments, a pressure sensor and/or an intravascular ultrasound (IVUS) transducer can be added to or incorporated into a delivery system and method for use with any of the filters described herein. The pressure sensor can be used to measure the pressure at various positions within the vasculature, which can be used to determine blood flow, while the intravascular ultrasound (IVUS) transducer can be used to measure fluid flow and/or provide imaging within the vessel. These activities can be performed in cooperation with any of the filter embodiments described herein. In some embodiments, the pressure sensor and/or IVUS transducer can be incorporated into the guidewire at one or more locations, such as the distal end or distal portion of a guidewire, as described in U.S. Pat. Nos. 8,277,386, 6,106,476 and 6,780,157 which are hereby incorporated by reference in their entireties for all purposes, as well as being incorporated into intermediate and proximal portions of the guidewire. The guidewire with the pressure sensor and/or the IVUS transducer can be used much like a normal guidewire to help navigate the delivery device through the vasculature, with the added benefit of providing pressure measurements and ultrasound imaging to help in the navigation, to visualize the device placement site, and to monitor and ensure proper device deployment. In some embodiments, the IVUS transducer generates image slices as it is advanced and retracted which can then be assembled together to form a three dimensional reconstruction of the vasculature and/or the device within the vasculature. In some embodiments, the guidewire with the pressure sensor and/or IVUS transducer can be fastened to a catheter in a similar manner to that described below for a catheter having a pressure sensor and/or IVUS transducer that is fastened to another catheter.

FIGS. 34A-34C illustrate an example of a guidewire X100 having both a pressure sensor X102 and an IVUS transducer X104 located at the distal portion of the guidewire X100. In some embodiments, the pressure sensor X102 can be made from a semiconductor material, such as silicon, that is formed into a diaphragm and can be located proximally of the distal tip, while the IVUS transducer X104 can be located at the distal tip of the guidewire X104.

In some embodiments, the pressure sensor and/or IVUS transducer can be located on a catheter in a similar configuration to the guidewire. For example, the IVUS transducer can be located on the distal tip of the catheter while the pressure sensor(s) can be located proximally of the IVUS transducer at one or more locations along the catheter body, from the distal portion of the catheter to an intermediate portion of the catheter to the proximal portion of the catheter. The pressure and/or imaging catheter can be used in parallel with the delivery or retrieval device or any other catheter that is inserted into the vasculature. In some embodiments, the pressure and/or imaging catheter can be fastened to the delivery or retrieval device or other catheter by, for example, enclosing both catheters in a sheath or larger catheter or by fusing the two catheters together. For example, U.S. Pat. Nos. 6,645,152 and 6,440,077, both to Jung et al. and hereby incorporated by reference in their entireties for all purposes, discloses an intravascular ultrasound catheter joined together in parallel with a vena cava filter delivery device to guide placement of the filter in the vena cava. The pressure and/or imaging catheter can be used for the same purposes as the pressure and/or imaging guidewire.

FIGS. 35A-35D illustrate two embodiments of an intravascular ultrasound catheter X200 joined together in parallel with a catheter X202 that can be used, for example, to deliver a device to a location with the vasculature, such as a vena cava filter to the vena cava. The intravascular ultrasound catheter X200 can have an IVUS transducer X204 located on the distal portion of the IVUS catheter X200. The IVUS transducer X204 can be a solid state transducer that is disk shaped or cylindrically shaped with a hole to allow passage of a guidewire X206 or other device through the IVUS catheter X200. As shown in FIGS. 35A and 35B, the IVUS catheter X200 and the delivery catheter X202 can be joined together in parallel without a sheath by adhering or fusing the two catheters together. FIGS. 35C and 35D illustrate the same IVUS catheter X200 and delivery catheter X202 fastened together using a sheath X208.

In some embodiments as illustrated in FIGS. 36A and 36B, the pressure sensor and/or IVUS transducer can be integrated into the delivery or retrieval catheter X300 or device itself. In one aspect, the device is any of the filters having enhanced capabilities described herein. For example, the IVUS transducer X302 can be integrated into the distal tip or end of the catheter X300 or device. The pressure sensor X304 can be located on a distal portion of the catheter shaft proximally of the IVUS transducer X302. A wire can extend from the IVUS transducer X302 and/or pressure sensor X304 to one or more connectors X306 located at the proximal end of the catheter X300. The connector(s) X306 can be used to connect the IVUS transducer X302 and/or pressure sensor X304 to an imaging system and/or processing system. In the illustrated embodiment, the catheter X300 can be used to deliver a vena cava filter X308 to the vena cava. The catheter X300 can additionally have a telescoping sleeve or pusher rod to deploy the vena cava filter X308, or alternatively, the outer catheter sheath can be retracted to deployed the filter. The IVUS transducer can provide positioning guidance and determine the relative location of the filter by advancing and retracting the IVUS transducer X302 on the catheter X300 to generate a plurality of image slices that can be assembled to reconstruct a three dimensional image.

Use of the ultrasound imaging system allows the operator to deliver the device without fluoroscopy or using less fluoroscopy, thereby reducing the radiation exposure to the patient, while allowing more accurate evaluation of the vasculature, aiding placement of the device and allowing confirmation that device placement was proper. The imaging can be used to aid in the deployment of the filters or other devices. The vasculature and implant location can be imaged prior to deployment, after deployment and/or during deployment. The imaging can be used to aid in positioning of the filter or device within the vasculature. The imaging can be used to image the deployment location and determine the appropriate sizing of the filter or other device. The imaging can be used to help estimate treatment duration.

Although an imaging systems described above have been ultrasound based, other imaging systems can be used instead or in addition. For example, the imaging system can be based on intravascular ultrasound (IVUS), Forward-Looking IVUS (FLIVUS), optical coherence tomography (OCT), piezoelectric micro-machined ultrasound traducer (PMUT), and FACT.

Additional aspects of the formation and use of echogenic materials is made with reference to the following US Patents and Patent Publications, each of which is incorporated herein by reference in its entirety: US 2010/0130963; U.S. Pat. Nos. 5,921,933; 4,276,885; 4,572,203; 4,718,433; 4,442,843; 5,327,891; 4,401,124; 4,265,251; 4,466,442; 4,718,433; 5,081,997; 5,289,831; and 5,201,314. Additional details of various filter designs described herein may be obtained with reference to the following U.S. Pat. Nos. 3,952,747; 4.817,600; 5,059,205; 5,242,462; 6,620,183; 6,217,600; 8,273,099; 4,494,531; 4,425,908; 4,832,055; 5,133,733; 3,540,431; 5,344,427; 5,725,550; 4,619,246; 4,990,156; 5,234,458; and 4,643,184, each of which is incorporated herein by reference in its entirety. 

What is claimed is:
 1. A filter comprising: a hub; and a plurality of legs or wires or segments extending from the hub; wherein the plurality of legs or wires or segments comprise a first section having a first pattern of voids formed therein to provide an enhanced echogenic characteristic of the first section and a second section having a second pattern of voids formed therein to provide an enhanced echogenic characteristic of the second section, wherein the first pattern of voids is different than the second pattern of voids.
 2. The filter of claim 1 wherein the first pattern of voids is filled with air.
 3. The filter of claim 2 wherein the second pattern of voids is filled with air.
 4. The filter of claim 2 wherein the second pattern of voids is filled with an echogenic material.
 5. The filter of claim 1 wherein the first pattern of voids is filled with an echogenic material.
 6. The filter of claim 1 wherein the first pattern of voids are air bubbles formed within the first section.
 7. The filter of claim 1 wherein the first pattern of voids are air bubbles formed within an ePTFE material forming the first section of the portion of one or more of the legs or wires or segments.
 8. The filter of claim 1 wherein the first pattern of voids is scaled to a suitable size, shape and orientation for use with an intravascular ultrasound system.
 9. The filter of claim 1 further comprising at least one fixation element and wherein the fixation element comprises a third pattern of voids to provide an enhanced echogenic characteristic of the at least one fixation element or the filter.
 10. A filter comprising: a hub; and a plurality of segments extending from the hub, wherein a first of the plurality of segments comprises a first pattern of voids formed therein to provide an enhanced echogenic characteristic of the first of the plurality of segments, wherein a second of the plurality of segments comprises a second pattern of voids formed therein to provide an enhanced echogenic characteristic of the second of the plurality of segments, wherein the first pattern is different than the second pattern.
 11. The filter of claim 10 wherein the first pattern of voids comprise an air gap formed in the first segment.
 12. The filter of claim 11 wherein the second pattern of voids comprises an air gap formed in the second segment.
 13. The filter of claim 11 wherein the second pattern of voids is filled with an echogenic material.
 14. The filter of claim 10 wherein the first pattern of voids comprise a gap formed in the first segment, wherein the gap is filled with an echogenic material.
 15. The filter of claim 10 wherein the first pattern of voids comprises an air pocket in an ePTFE material. 